Unique Neurophysiological Vulnerability of Visual Attention Networks to Acute Inflammation

Abstract

Highlights• Typhoid vaccination induced a transient mild inflammatory state • Mild inflammation alters neurophysiological process associated with attention • Mild inflammation selectively increased alerting-related alpha suppression while behavior was unaffected • A greater inflammatory response was correlated with more alpha suppression ABSTRACT Illness is often accompanied by perceived cognitive sluggishness, a symptom that may stem from immune system activation. The current study used electroencephalography (EEG) to assess how inflammation affected three different distinct attentional processes:alerting, orienting and executive control. In a double-blinded placebo-controlled withinsubjects design (20 healthy males, mean age = 24.5, SD = 3.4), Salmonella typhoid vaccination (0.025 mg; Typhim Vi, Sanofi Pasteur) was used to induce transient mild inflammation, while a saline injection served as a placebo-control. Participants completed the Attention Network Test with concurrent EEG recorded six hours post-injection. Analyses focused on behavioral task performance and on modulation of oscillatory EEG activity in the alpha band (9-12 Hz) for alerting as well as orienting attention and frontal theta band (4-8 Hz)for executive control. Vaccination induced mild systemic inflammation, as assessed by interleukin-6 (IL-6) levels. While no behavioral task performance differences between the inflammation and placebo condition were evident, inflammation caused significant alterations to task-related brain activity. Specifically, inflammation produced greater cue-induced suppression of alpha power in the alerting aspect of attention while individual variation in the inflammatory response was significantly correlated with the degree of alpha power suppression. Notably, inflammation did not affect orienting (i.e., alpha lateralization) or executive control (i.e., frontal theta activity). These results reveal a unique neurophysiological vulnerability to acute mild inflammation of the neural network that underpins attentional alerting functions. Observed in the absence of performance decrements, these novel findings suggest that acute inflammation requires individuals to exert greater cognitive effort when preparing for a task in order to maintain adequate behavioral performance.A repeated measures ANOVA with cue (left, right), time (early, late), and injection condition (placebo, vaccine) was conducted to assess the effect of injection condition on the ALI.Levene's test of Equality of Variances and Mauchly's Test of Sphericity were used to test for assumption violations with adjustments made using the Greenhouse-Geisser corrections;Bonferroni corrections were applied to post-hoc pairwise comparisons (two-tailed unless stated otherwise) to control for type I error rate; and alpha was set at .05. RESULTS Physiological responsesEq 1.1 Eq 1.2